Poly(Ester Amide) Macromers and Polymers Thereof

ABSTRACT

Amino acid-based poly(ester amide) (PEA) macromers (e.g., functional PEA macromers) and methods for preparing amino acid-based poly(ester amide) (PEA) macromers. The functional PEA macromers can comprise functional groups such as hydroxyl, amine, sulfonic acids, carboxyl, thiol and acryloyl at the two terminuses of the PEA macromers. The content of the terminal functional groups on the macromers can be precisely controlled by adjusting the molar ratio of reactive monomers. The resulting versatility of these new functional PEA macromers can be used to fabricate a wide range of PEAs and PEA hybrid derivatives with very different chemical, physical, mechanical, thermal and biological properties. The functional PEA macromers can also be polycondensed into forming block PEA polymers.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. provisional patent applicationNo. 61/311,845, filed Mar. 9, 2010, the disclosure of which isincorporated herein by reference.

FIELD OF THE INVENTION

The present invention generally relates to poly(ester amide) (PEA)based-macromers and polymers of PEA-based macromers. More particularly,the present invention relates to poly(ester amide) macromers and methodsof making and using such macromers and polymers.

BACKGROUND OF THE INVENTION

Amino acid-based biodegradable PEAs have been studied for many years dueto their biocompatibility, biodegradability and mechanical properties.The presence of amide and ester bonds in PEA furnishes the PEA with acombination of properties typically exhibited by either polyesters orpolyamides. Biodegradable PEA is typically synthesized by a solutionpolycondensation reaction of a-amino acids, aliphatic dicarboxylic acids(or dichloride of dicarboxylic acids) and diols (see Guo et al., Journalof Polymer Science, Part A: Polymer Chemistry 2007, 45(9): 1595-1606).

PEA homopolymers generally do not have any functional groups locatedeither along the PEA backbone chain or as pendant groups. The firstreported synthesis of functional PEAs was based on a copolymer approach.A free functional group in the form of a carboxylic acid group wasintroduced in the lysine segment of the PEA copolymer. (See, Jokhadze etal., Journal of Biomaterials Science—Polymer Edition 2007;18(4):411-438.) In another approach, carbon-to-carbon double bonds havebeen positioned along the backbone of PEA to provide a reactive site forthe introduction of a functional group into PEA via unsaturated diacidsand/or diols.

Delivery of desired biomolecules to cells can be accomplished by variousdelivery means that generally fall into 4 broad categories: watersoluble cationic polymers, lipids, dendrimers and nanoparticles. Amongthem, the water soluble synthetic and natural polycations have attractedthe most attention. A large number of cationic polymers have been testedfor gene delivery. Among them, poly-L-lysine (PLL) and polyethylenimine(PEI) have been intensively studied because of their strong interactionwith the plasmid DNA which results in formation of a compact polymer/DNAcomplex. Other synthetic and natural polycations developed as non-viralvectors includes polyamidoamine dendrimers and chitosan,imidazole-containing polymers with proton-sponge effect,membrane-disruptive peptides and polymers like polyethylacrylic acid(PEAA), poly [alpha-(4-aminobutyl)-L-glycolic acid] (PAGA), and poly(amino acid) based materials. However, most of them could not achieveboth high transfection efficiency and low toxicity.

BRIEF SUMMARY OF THE INVENTION

In an aspect, the present invention provides PEA macromers having thefollowing structure:

where R¹ and R² at each occurrence in the macromer are independentlyselected from a C₁ to C₂₀ alkyl group, C₂ to C₂₀ alkenyl group, C₁ toC₂₀ alkyl diol group and C₄ to C₂₀ alkyl ether group, R³ is selectedfrom a C₁ to C₂₀ alkyl group, C₂ to C₂₀ alkenyl group, C₂ to C₂₀ alkyldiol group and C₄ to C₂₀ alkyl ether group, R⁴ and R⁵ at each occurrencein the macromer are independently a side-group of a naturally occurringamino acid or non-naturally occurring amino acid, E¹ and E² are eachindependently an end group, and n is an integer from 1 to 20.

In an aspect, the present invention provides a method for making apoly(ester amide) polymer comprising the steps of: a) mixing a firstmacromer having the following structure:

where E¹ and E² are each a —COOH group, and a second macromer having thefollowing structure:

where E¹ and E² are each independently a —NH₂ group or —OH group, in aratio of first macromer:second macromer of, for example, 0.5:1 to 2:1,and optionally, a solvent; and b) mixing the mixture from a) with adehydrating agent until polymerization has proceeded to the desiredextent. In an embodiment, the present invention provides polymers madeby this method.

In an aspect, the present invention provides a poly(ester amide) polymerhaving the following structure:

where n at each occurrence in the polymer is an integer from 1 to 20,and m is an integer from 2 to 100. In various embodiments, a poly(esteramide) polymer has one the following structures:

In an aspect, the present invention provides a macromer having thefollowing structure:

where R⁶ and R⁷ at each occurrence in the macromer are independentlyselected from a C₁ to C₂₀ alkyl group, C₂ to C₂₀ alkenyl group, C₁ toC₂₀ alkyl diol group and C₄ to C₂₀ alkyl ether group, R⁸ is a C₁ to C₂₀alkyl group, C₂ to C₂₀ alkenyl group, C₁ to C₂₀ alkyl diol group and C₄to C₂₀ alkyl ether group, R⁹ and R¹⁰ at each occurrence in the macromerare independently a side-group of a naturally occurring amino acid or anon-naturally occurring amino acid, R¹¹ ″ and R¹² are each independentlya side-group of a naturally occurring amino acid or a non-naturallyoccurring amino acid, E³ and E⁴ are each independently an end group, andj is an integer from 1 to 20.

In an embodiment, a macromer has the following structure:

where p is an integer from 1 to 20, q is an integer from 1 to 20, and ris an integer from 1 to 20.

In an aspect, the present invention provides a method for making apoly(ester amide) polymer comprising the steps of: a) mixing a firstmacromer having the following structure:

where E³ and E⁴ are each a —COOH, and a second macromer having thefollowing structure:

where E³ and E⁴ are each independetly a —NH₂ group or —OH group, in aratio of first macromer:second macromer of, for example, 0.5:1 to 2:1,and optionally, a solvent; and b) mixing the mixture from a) with adehydrating agent until polymerization has proceeded to the desiredextent. In an embodiment, the present invention provides polymers madeby this method.

In an aspect, the present invention provides a poly(ester amide) polymerhaving the following structure:

where L³ and L⁴ at each occurrence in the polymer are independently anNH-linking group or 0-linking group, and k is an integer from 2 to 100.

In an aspect, the present invention provides a method for making apoly(ester amide) copolymer comprising the steps of:

a) mixing a first macromer having the following structure:

where E¹ and E² are each a —COOH group, and a second macromer having thefollowing structure:

where E³ and E⁴ are each independently a —NH₂ group or —OH group, ormixing a first macromer having the following structure:

where E³ and E⁴ are each a —COOH group, and a second macromer having thefollowing structure:

where E¹ and E² are independently a —NH₂ group or —OH group, in a ratioof first macromer:second macromer of, for example, 0.5:1 to 2:1, andoptionally, a solvent; and b) mixing the mixture from a) with adehydrating agent until polymerization has proceeded to the desiredextent. In an embodiment, the present invention provides polymers madeby this method.

In an aspect, the present invention provides a poly(ester amide)copolymer having the following structure:

where R¹³, R¹⁴, R¹⁵, R¹⁶, R¹⁷, R¹⁸, R²⁵, R²⁶, R²⁷, R²⁸, R²⁹ and R³⁰ ateach occurrence in the polymer are independently selected from a C₁ toC₂₀ alkyl group, C₂ to C₂₀ alkenyl group, C₁ to C₂₀ alkyl diol group andC₄ to C₂₀ alkyl ether group, R¹⁹, R²⁰, R²¹, R²², R²³, R²⁴ and R³¹, R³²,R³³, R³⁴, R³⁵ and R³⁶ at each occurrence in the polymer areindependently a side-group of a naturally occurring amino acid or anon-naturally occurring amino acid, L⁵, L⁶, L⁷ and L⁸ at each occurrencein the polymer are independently an NH-linking group or O-linking group,E⁵, E⁶, E⁷ and E⁸ are each independently an end group, a at eachoccurrence in the polymer is an integer from 1 to 20, b at eachoccurrence in the polymer is an integer from 1 to 20, d at eachoccurrence in the polymer is an integer from 1 to 20, e at eachoccurrence in the polymer is an integer from 1 to 20, c is an integerfrom 2 to 100, and f is an integer from 2 to 100.

In an aspect, the present invention provides a composition comprising amacromer or polymer as disclosed herein. In an embodiment, a compositionis a hydrogel or gel. For example, a hydrogel or gel is formed byphotochemical reaction of a macromer or polymer disclosed herein and agel-forming compound (e.g., PEG-DA). In an embodiment, the compositionfurther comprises a drug, a biological agent, nutrient, peptide,polynucleotide, or a combination thereof.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 (Scheme 1). Synthesis of Macromer 1.1 intermediate and Macromer1.2 from NPEG and Phe4EG.

FIG. 2. Synthesis of Polyglycol 250 Acid Dichloride.

FIG. 3. Synthesis of Di-p-nitrophenyl ester of Polyglycol 250 Diacid(NPEG) monomer.

FIG. 4. Synthesis of Di-p-toluenesulfonic Acid Salts ofBis-L-phenylalanine Tetraethylene Glycol Ester (Phe4EG) monomer.

FIG. 5. ¹H NMR spectra of Macromer 1.1 intermediate and Macromer 1.

FIG. 6 (Scheme 2). Synthesis of Macromer 2.1 intermediate, Macromer 2.2and Macromer 2.3.

FIG. 7. Synthesis of Di-p-toluenesulfonic Acid Salt ofBis-L-phenylalanine Butane-1,4-diester Monomer (Phe-4).

FIG. 8. Synthesis of Di-p-nitrophenyl Sebacate Monomer (NS).

FIG. 9. ¹H NMR spectra of NS, Macromer 2.1 intermediate, Macromer 2.2and Macromer 2.3.

FIG. 10. FTIR spectra of Macromer 2.1 intermediate, Macromer 2.2 andMacromer 2.3. The >C═C< stretch of Macromer 2.3 at 1638 cm⁻¹ has beenoverlapped, CH₂ of vinyl tag at 810 cm⁻¹.

FIG. 11. Gel made from Macromer 2.3 (self-gelation without non-PEAcomponent).

FIG. 12 (Scheme 3.1). Synthesis of additional functional macromershaving a wide range of functional end-groups from Macromer 2.1 (or 1.1).

FIG. 13 (Scheme 3.2). Preparation of higher molecular weight PEAhomopolymers and copolymers.

FIG. 14 (Scheme 4). Synthesis of Macromer 4.1 and Macromer 4.2.

FIG. 15. Synthesis of Di-p-nitrophenyl Fumarate Monomer (NF).

FIG. 16. ¹H NMR spectra of Macromer 4.1 and Macromer 4.2.

FIG. 17. Hybrid gel made from sulfonic acid-terminated unsaturatedfunctional PEA Macromer 4.2 and PEG-750 diacrylate.

FIG. 18 (Scheme 5). Synthesis of Macromer 5.1, Macromer 5.2 and

Macromer 5.3.

FIG. 19. Synthesis of Di-p-toluenesulfonic Acid Salt of Bis-L-arginineButane-1,4-diester Monomer (Arg-4-S).

FIG. 20 (Scheme 6). Synthesis of Macromer 6.1 and Macromer 6.2.

FIG. 21. ¹H NMR spectrum of Macromer 6.2.

FIG. 22 (Scheme 7). Synthesis of Arg-Based Macromer (III) withfunctional double bond end groups.

FIG. 23. ¹H NMR spectrum of Macromer 7.2.

FIG. 24. Hybrid gel made from Macromer 7.2 and PEA-750 diacrylate.

FIG. 25 (Scheme 8). Synthesis of Monomer 8.1.

FIG. 26. ¹H NMR spectrum of Macromer 8.1.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides new amino acid-based poly(ester amide)(PEA) macromers (also referred to as functional PEA macromers) andpolymers thereof. The present invention also provides methods ofpreparing and uses of such amino acid-based PEA macromers and polymersthereof.

The functional PEA macromers comprise functional groups such ashydroxyl, amine, sulfonic acids, carboxyl, thiol and acryloyl at the twoterminals of the PEA macromer. The content of the terminal functionalgroups of the macromers can be controlled by adjusting the molar ratioof reactive monomers.

The versatility of the functional PEA macromers can be used to fabricatea wide range of PEAs and PEA hybrid derivatives with different chemical,physical, mechanical, thermal and biological properties. The functionalPEA macromers can also be polycondensed into forming block PEA polymers.

The alkyl groups of the present invention have, for example, from 1carbon to 20 carbon atoms, including all ranges and integerstherebetween. The alkyl groups can be substituted or unsubstituted. Thealkyl groups can also be branched or linear. In an embodiment, the alkylgroup is a C₁ to C₂₀ alkyl group that has from 1 carbon to 20 carbons,including all ranges and integers therebetween.

The alkenyl groups of the present invention have, for example, at leastone carbon-carbon double bond. The alkenyl group can have from 2 carbonatoms to 20 carbon atoms, including all ranges and integerstherebetween. The alkenyl group can be substituted or unsubstituted. Thealkenyl groups can also be branched or linear. In an embodiment, thealkenyl group is a C₂ to C₂₀ alkenyl group that has from 2 carbons to 20carbons, including all ranges and integers therebetween.

As used herein, the term “alkyl diol group” means a group comprising analkyl moiety and at least two oxygen moities. An example of such a groupis —O—(CH₂)_(n)—O—. The alkyl moiety diol group can have from 1 carbonatoms to 20 carbon atoms, including all ranges and integerstherebetween. The alkyl moiety can be substituted or unsubstituted. Thealkyl moiety can also be branched or linear. In an embodiment, the alkyldiol group is a C₁ to C₂₀ alkyl diol group that has from 1 carbons to 20carbons, including all ranges and integers therebetween.

As used herein, the term “alkyl ether group” means a group comprised ofat least one alkyl ether moiety. An example of an alkyl ether moiety is—O—CH₂)_(n)—, where n is an integer from 1 to 8, including all rangesand integers therebetween. The alkyl ether group can have from 2 carbonsto 20 carbons, including all ranges and integers therebetween. The alkylether group comprises from 1 to 10, including all ranges and integerstherebetween, alkyl ether moieties. The alkyl moiety of the alkyl ethermoiety group can have from 1 carbon atoms to 10 carbon atoms, includingall ranges and integers therebetween. The alkyl moiety can besubstituted or unsubstituted. The alkyl moiety can also be branched orlinear. In an embodiment, the alkyl ether group is a C₄ to C₂₀ alkylether group that has from 4 carbons to 20 carbons, including all rangesand integers therebetween. In an embodiment, the alkyl ether moiety is—O—(CH₂)₂—.

As used herein, the term “side-group of a naturally occurring aminoacid” means any side-chain from a naturally occurring amino acid (e.g.,H— from glycine, CH₃— from alanine, CH₂-Ph from phenylalanine, and analkylguanidinium group from arginine, and the like). In variousembodiments, the side-group of a naturally occurring amino acid is theside group of one of the 22 naturally occurring amino acids.

As used herein, the term “side group of a non-naturally occurring aminoacid” means any side chain from synthetic non-naturally occurring aminoacids (also referred to as non-standard amino acids). Examples of sidegroups of non-naturally occurring amino acids not found in naturallyoccurring amino acids include, but are not limited to, alkenyl groups(e.g., substituted and unsubstituted, and branched and linear)comprising at least one carbon-carbon double bond and having from 3carbons to 10 carbons (including all ranges and integers therebetween),alkyl groups (e.g., substituted and unsubstituted, and branched andlinear), and aryl groups (e.g., substituted and unsubstituted). Anexample of a non-naturally occurring amino acid is allyl glycine.

As used herein the term “end group” means a group which terminates a PEAmacromer or polymer. In various embodiments, it is desirable that theend group have at least one functional group (e.g., —F, —Cl, —C═C—, —OH,—NH₂, —C(O)OH, —C(O)NH₂, —SH, and the like), which can be covalentlybonded to the PEA macromer or polymer via an alkyl group. Examples ofsuch groups include, but are not limited to, hydrogen, nitrophenylgroup, —NH-alkenyl (C₂-C₁₀)group, —-NH-alkynyl (C₂-C₁₀)group, —NH-alkyl(C₂-C₁₀)thio group, —NH-alkyl (C₂-C₁₀)hydroxyl group, —NH-alkyl amino(C₂-C₁₀)group, NH-alkyl (C₂-C₁₀)carboxyl group and NH-alkyl (C₂-C₁₀)halosubstituted group.

As used herein, the term “linking group” (e.g., L¹ and L²) is any groupwhich covalently bonds (i.e., joins) adjacent macromer units in apolymer. Such a group is formed from a polymerization reaction betweentwo macromers functionalized with groups which can react to form thelinking group. Examples of linking groups include, but are not limitedto, —NH₂— and —C(O)O—. In an embodiment, monomers are functionalizedwith groups such that on polymerization of two monomers a linking groupis formed.

In an aspect, the present invention provides functional PEA macromers.The macromers of the present invention can be made, for example, byreaction of two monomers as shown in FIGS. 1, 6, 14, 18, 20 and 25.

In an embodiment, a PEA macromer has the following structure:

In this embodiment, R¹ and R², at each occurrence in the macromer, areindependently selected from a C₁ to C₂₀ alkyl group, C₂ to C₂₀ alkenylgroup, C₁ to C₂₀ alkyl diol group and C₄ to C₂₀ alkyl ether group; R³ isselected from a C₁ to C₂₀ alkyl group, C₂ to C₂₀ alkenyl group, C₂ toC₂₀ alkyl diol group and C₄ to C₂₀ alkyl ether group; R⁴ and R⁵ at eachoccurrence in the macromer are independently a side-group of a naturallyoccurring amino acid or non-naturally occurring amino acid, E¹ and E²are each independently an end group, and n is an integer from 1 to 20,including all ranges and integers therebetween. In an embodiment, R¹=R³and/or R⁴ =R⁵.

Examples of macromers of this embodiment include, but are not limitedto, macromers with the following structures:

In these examples, x is an integer from 1 to 10, including all rangesand integers therebetween, y is an integer from 1 to 10, including allranges and integers therebetween, z is an integer from 1 to 10,including all ranges and integers therebetween, u is an integer from 1to 20, including all ranges and integers therebetween, v is an integerfrom 1 to 20, including all ranges and integers therebetween, w is aninteger from 1 to 20, including all ranges and integers therebetween,and t is an integer from 1 to 20, including all ranges and integerstherebetween.

In another embodiment, a macromer has the following structure:

In this embodiment, R⁶ and R⁷, at each occurrence in the macromer, areindependently selected from a C₁ to C₂₀ alkyl group, C₂ to C₂₀ alkenylgroup, C₁ to C₂₀ alkyl diol group and C₄ to C₂₀ alkyl ether group, R⁸ isa C₁ to C₂₀ alkyl group, C₂ to C₂₀ alkenyl group, C₁ to C₂₀ alkyl diolgroup and C₄ to C₂₀ alkyl ether group, R⁹ and R¹⁰ at each occurrence inthe macromer are independently a side-group of a naturally occurringamino acid or a non-naturally occurring amino acid, R¹¹ and R¹² are eachindependently a side-group of a naturally occurring amino acid or anon-naturally occurring amino acid, E³ and E⁴ are each independently anend group, and j is an integer from 1 to 20, including all ranges andintegers therebetween. In an embodiment, R⁶=R⁸ and/or R⁹=R¹⁰=R¹¹=R¹².

Examples of macromers of this embodiment include, but are not limitedto, macromers with the following structures:

wherein p is an integer from 1 to 20, including all ranges and integerstherebetween, q is an integer from 1 to 20, including all ranges andintegers therebetween, and r is an integer from 1 to 20, including allranges and integers therebetween.

The PEA macromers of the present invention can have a range of numberaveraged molecular weights, M_(n), and a weight averaged molecularweights, M_(w). For example, the macromers can have a M_(n) of from 0.4kg/mol to 100 kg/mol, including all integers and ranges to the 0.1kg/mol therebetween. For example, the macromers can have a M_(w) of from0.4 kg/mol to 100 kg/mol, including all integers and ranges to the 0.1kg/mol therebetween. The M_(n) and/or M_(w) of the macromers can bedetermined by, for example, gel permeation chromatography.

In an embodiment, the PEA macromers (or polymers of PEA macromers) haveone or more counter-ions (e.g., having a pKa from about −7 to +5)associated with positively charged groups (e.g., the alkyl guanidiniumgroup of arginine) therein. Examples of counter-ions suitable toassociate with the macromers or polymers of the invention compositionare counter-anions of weak acids. Examples of such counter-anionsinclude CH₃COO⁻, CF₃COO⁻, CCl₃COO⁻, Tos⁻(Tos=p-toluene sulfonic acid,ester) and the like. Other examples of suitable counter ions includehalides, such as F, Cl⁻ and Br⁻, sulfate and nitrate. In one embodiment,macromers or polymers have one or more ammonium groups that are presentas a halide, Tos⁻, acetate, halogen-substituted acetate, sulfate,nitrate, or a combination thereof, salt.

In an embodiment, the functional PEA macromer has photo-crosslinkable—C═C— bonds at least one of the two end groups of the PEA macromer. Thismonomer can be used, for example, as a cross-linker forphoto-crosslinking or/and for making copolymers having PEA segmentsusing photo-crosslinking

In an aspect, the present invention provides PEA polymers comprising PEAmacromer and methods of making such polymers. The polymers of thepresent invention can be made by polymerization of macromers of thepresent invention. The PEA polymers can be homopolymers or copolymers.

FIG. 13 (Scheme 3.2) shows preparation of higher molecular weight PEAhomopolymers and copolymers. For example, as shown in FIG. 13 (Scheme3.2), HOOC-Macromer-COOH and H₂N-Macromer-NH₂ (or OH-Macromer-OH) canpolycondense together under dehydrating agent to form a higher molecularweight PEA homopolymer or a copolymer (e.g., if the two functionalmacromers have different PEA backbones, prepared from different aminoacids). Also as shown in FIG. 13 (Scheme 3.2), HOOC-Macromer-COOHfunctional macromer can act as a macromer cross-linker to cross-linkfunctional PEA with a pendant —NH₂ group in the presence of dehydratingagent. (see, e.g., Deng et al., Biomacromolecules 10 (11), 3037-3047).H₂N-Macromer-NH₂ functional macromer can also act as a macromercross-linker to cross-link functional PEAs having pendant —COOH group(such as those disclosed in U.S. Pat. No. 6,503,538) in the presence ofdehydrating agent.

In an embodiment, a PEA polymer has the following structure:

In this embodiment, R¹ and R² at each occurrence in the polymer areindependently selected from a C₁ to C₂₀ alkyl group, C₂ to C₂₀ alkenylgroup, C₁ to C₂₀ alkyl diol group and C₄ to C₂₀ alkyl ether group, R³ isselected from a C₁ to C₂₀ alkyl group, C₂ to C₂₀ alkenyl group, C₁ toC₂₀ alkyl diol group and C₄ to C₂₀ alkyl ether group, R⁴ and R⁵ at eachoccurrence in the polymer are each independently a side-group of anaturally occurring amino acid or a non-naturally occurring amino acid,L¹ and L² at each occurrence in the polymer are independently anNH-linking group or O-linking group, E¹ and E² are each independently anend group, and n at each occurrence in the polymer is an integer from 1to 20, including all ranges and integers therebetween, and m is aninteger from 2 to 100, including all ranges and integers therebetween.In an embodiment, R¹=R³ and/or R⁴=R⁵.

In an embodiment, a PEA polymer of has the following structure:

PEA polymers of the above embodiments can be made by polymerization ofthe appropriate macromers of the present invention. In an embodiment, amethod for making such polymers comprises the steps of: a) mixing afirst macromer having the following structure:

R¹ and R² at each occurrence in the macromer are independently selectedfrom a C₁ to C₂₀ alkyl group, C₂ to C₂₀ alkenyl group, C₁ to C₂₀ alkyldiol group and C₄ to C₂₀ alkyl ether group, R³ is selected from a C₁ toC₂₀ alkyl group, C₂ to C₂₀ alkenyl group, C₁ to C₂₀ alkyl diol group andC₄ to C₂₀ alkyl ether group, R⁴ and R⁵ at each occurrence in themacromer are independently a side-group of a naturally occurring aminoacid or a non-naturally occurring amino acid, E¹ and E² are each a -COOHgroup, and n is an integer from 1 to 20, including all ranges andintegers therebetween, anda second macromer having the following structure:

R¹ and R² at each occurrence in the macromer are independently selectedfrom a C₁ to C₂₀ alkyl group, C₂ to C₂₀ alkenyl group, C₁ to C₂₀ alkyldiol group and C₄ to C₂₀ alkyl ether group, R³ is selected from a C₁ toC₂₀ alkyl group, C₂ to C₂₀ alkenyl group, C₁ to C₂₀ alkyl diol group andC₄ to C₂₀ alkyl ether group, R⁴ and R⁵ at each occurrence in themacromer are independently a side-group of a naturally occurring aminoacid or non-naturally occurring amino acid, E¹ and E² are eachindependently a —NH₂ group or —OH group, and n is an integer from 1 to20, including all ranges and integers therebetween, in a ratio of firstmacromer:second macromer of 0.5:1 to 2:1, including all ranges andvalues to 0.1 therebetween, and optionally, a solvent; and b) mixing themixture from a) with a dehydrating agent until polymerization hasproceeded to the desired extent.

The solvent can be any solvent in which the macromers and dehydratingagent can react. It is desirable that the macromers and dehydratingagent have sufficient solubility in the solvent such that apolymerization reaction can occur. Examples of suitable solventsinclude, but are not limited to, dimethylsulfoxide (DMSO),dimethylformamide (DMF), N,N-dimethylacetamide (DMA) and the like.

The dehydrating agent is any reagent which facilitates a reactionbetween macromers to form a linking group. Examples of such reagentsincludes, but is not limited to, N,N′-dicyclohexylcarbodiimide (DCC),N,N′-diisopropylcarbodiimide (DIC),1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC),N,N′-carbonyldiimidazole (CDI) and the like.

The reaction time is the time required for a polymerization reaction toproceed to the desired extent. In various embodiments, the reaction timeis the time required for the polymerization reaction to proceed suchthat at least 50%, 60%, 70%, 80%, 90%, 95% or 99% of monomers topolymerize.

In an embodiment, a PEA polymer has the following structure:

In this embodiment, R⁶, R⁷ and R⁸ at each occurrence in the polymer areindependently selected from a C₁ to C₂₀ alkyl group, C₂ to C₂₀ alkenylgroup, C₁ to C₂₀ alkyl diol group and C₄ to C₂₀ alkyl ether group, R⁹,R¹⁰, R¹¹ and R¹² at each occurrence in the macromer are independently aside-group of a naturally occurring amino acid or non-naturallyoccurring amino acid, L³ and L⁴ at each occurrence in the polymer areindependently an NH-linking group or O-linking group, E¹ and E² are eachindependently an end group, and j at each occurrence in the polymer isan integer from 1 to 20, including all ranges and integers therebetween,and k is an integer from 2 to 100, including all ranges and integerstherebetween. In an embodiment, R⁶=R⁸ and/or R⁹=R¹⁰=R¹¹=R¹².

PEA polymers of the above embodiment can be made by polymerization ofthe appropriate macromers of the present invention. In an embodiment, amethod for making a PEA polymer comprises the steps of: a) mixing afirst macromer having the following structure:

where R⁶ and R⁷, at each occurrence in the macromer, are independentlyselected from a C₁ to C₂₀ alkyl group, C₂ to C₂₀ alkenyl group, C₁ toC₂₀ alkyl diol group and C₄ to C₂₀ alkyl ether group, R⁸ is a C₁ to C₂₀alkyl group, C₂ to C₂₀ alkenyl group, C₁ to C₂₀ alkyl diol group and C₄to C₂₀ alkyl ether group, R⁹ and R¹° at each occurrence in the macromerare independently a side-group of a naturally occurring amino acid ornon-naturally occurring amino acid, R¹¹ and R¹² are each independently aside-group of a naturally occurring amino acid or non-naturallyoccurring amino acid, E³ and E⁴ are each a —COOH, and j is an integerfrom 1 to 20, including all ranges and integers therebetween, and asecond macromer having the following structure:

where R⁶ and R⁷, at each occurrence in the macromer are independentlyselected from a C₁ to C₂₀ alkyl group, C₂ to C₂₀ alkenyl group, C₁ toC₂₀ alkyl diol group and C₄ to C₂₀ alkyl ether group, R⁸ is a C₁ to C₂₀alkyl group, C₂ to C₂₀ alkenyl group, C₁ to C₂₀ alkyl diol group and C₄to C₂₀ alkyl ether group, R⁹ and R¹⁰ at each occurrence in the macromerare independently a side-group of a naturally occurring amino acid, R¹¹and R¹² are each independently a side-group of a naturally occurringamino acid, E³ and E⁴ are each independently a —NH₂ group or —OH group,and j is an integer from 1 to 20, including all ranges and integerstherebetween, in a ratio of first macromer:second macromer of 0.5:1 to2:1, including all ranges and values to 0.1 therebetween, andoptionally, a solvent; mixing the mixture from a) with a dehydratingagent until polymerization has proceeded to the desired extent.

In an embodiment, a PEA polymer is a copolymer having the followingstructure:

_(where R) ¹³, R¹⁴, R¹⁵, R¹⁶, R¹⁷, R¹⁸, R²⁵, R²⁶, R²⁷, R²⁸, R²⁹ and R³⁰,at each occurrence in the polymer, are independently selected from a C₁to C₂₀ alkyl group, C₂ to C₂₀ alkenyl group, C₁ to C₂₀ alkyl diol groupand C₄ to C₂₀ alkyl ether group, R¹⁹ , R²⁰, R²¹, R²², R²³, R²⁴ and R³¹,R³², R³³, R³⁴, R³⁵ and R³⁶ at each occurrence in the polymer areindependently a side-group of a naturally occurring amino acid or anon-naturally occurring amino acid, L⁵, L⁶, L⁷ and L⁸ at each occurrencein the polymer are independently an NH-linking group or O-linking group,E⁵, E⁶, E⁷ and E⁸ are each independently an end group, a at eachoccurrence in the polymer is an integer from 1 to 20, including allranges and integers therebetween, b at each occurrence in the polymer isan integer from 1 to 20, including all ranges and integers therebetween,d at each occurrence in the polymer is an integer from 1 to 20,including all ranges and integers therebetween, e at each occurrence inthe polymer is an integer from 1 to 20, including all ranges andintegers therebetween, c is an integer from 2 to 100, including allranges and integers therebetween, and f is an integer from 2 to 100,including all ranges and integers therebetween.

In the above embodiment, a method for making a PEA copolymer comprisesthe steps of: I) a) mixing a first macromer having the followingstructure:

R¹ and R², at each occurrence in the macromer, are independentlyselected from a C₁ to C₂₀ alkyl group, C₂ to C₂₀ alkenyl group, C₁ toC₂₀ alkyl diol group and C₄ to C₂₀ alkyl ether group, R³ is selectedfrom a C₁ to C₂₀ alkyl group, C₂ to C₂₀ alkenyl group, C₁ to C₂₀ alkyldiol group and C₄ to C₂₀ alkyl ether group, R⁴ and R⁵ at each occurrencein the macromer are independently a side-group of a naturally occurringamino acid or a non-naturally occurring amino acid, E¹ and E² are each a—COOH group, and n is an integer from 1 to 20, including all ranges andintegers therebetween, and a second macromer having the followingstructure:

where R⁶ and R⁷, at each occurrence in the macromer, are independentlyselected from a C₁ to C₂₀ alkyl group, C₂ to C₂₀ alkenyl group, C₁ toC₂₀ alkyl diol group and C₄ to C₂₀ alkyl ether group, R⁸ is a C₁ to C₂₀alkyl group, C₂ to C₂₀ alkenyl group, C₁ to C₂₀ alkyl diol group and C₄to C₂₀ alkyl ether group, R⁹ and R¹° at each occurrence in the macromerare independently a side-group of a naturally occurring amino acid or anon-naturally occurring amino acid, R¹¹ and R¹² are each independently aside-group of a naturally occurring amino acid or a non-naturallyoccurring amino acid, E³ and E⁴ are each independently a —NH₂ group or—OH group, and j is an integer from 1 to 20, including all ranges andintegers therebetween, or II) a) mixing a first macromer having thefollowing structure:

where R⁶ and R⁷ at each occurrence in the macromer are independentlyselected from a C₁ to C₂₀ alkyl group, C₂ to C₂₀ alkenyl group, C₁ toC₂₀ alkyl diol group and C₄ to C₂₀ alkyl ether group, R⁸ is a C₁ to C₂₀alkyl group, C₂ to C₂₀ alkenyl group, C₁ to C₂₀ alkyl diol group and C₄to C₂₀ alkyl ether group, R⁹ and R¹⁰ at each occurrence in the macromerare independently a side-group of a naturally occurring amino acid or anon-naturally occurring amino acid, R¹¹ and R¹² are each independently aside-group of a naturally occurring amino acid or a non-naturallyoccurring amino acid, E³ and E⁴ are each a —COOH group, and a secondmacromer having the following structure:

where R^(l) and R², at each occurrence in the macromer, areindependently selected from a C₁ to C₂₀ alkyl group, C₂ to C₂₀ alkenylgroup, C₁ to C₂₀ alkyl diol group and C₄ to C₂₀ alkyl ether group, R³ isselected from a C₁ to C₂₀ alkyl group, C₂ to C₂₀ alkenyl group, C₁ toC₂₀ alkyl diol group and C₄ to C₂₀ alkyl ether group, R⁴ and R⁵ at eachoccurrence in the macromer are independently a side-group of a naturallyoccurring amino acid or a non-naturally occurring amino acid, E¹ and E²are independently a —NH₂ group or —OH group, and n is an integer from 1to 20, including all ranges and integers therebetween, in a ratio offirst macromer:second macromer of 0.5:1 to 2:1, including all ranges andvalues to 0.1 therebetween, and optionally, a solvent; and mixing themixture from a) with a dehydrating agent until polymerization hasproceeded to the desired extent.

The PEA polymers of the present invention can have a range of numberaveraged molecular weights, M_(n), and a weight averaged molecularweights, M_(w). For example, the polymers can have a M_(n) of from 0.4kg/mol to 100 kg/mol, including all integers and ranges to the 0.1kg/mol therebetween. For example, the polymers can have a M_(w) of from0.4 kg/mol to 100 kg/mol, including all integers and ranges to the 0.1kg/mol therebetween. The M_(n) and/or M_(w), of the polymers can bedetermined by, for example, gel permeation chromatography.

In an aspect, the present invention provides compositions comprising thePEA macromers and PEA polymers of the present invention. In anembodiment, a composition is provided comprising a low MW nitrophenolend-capped PEA macromer wherein the backbone portion of the nitrophenolend-capped PEA macromer comprises a complete PEA. A method forsynthesizing a low MW nitrophenol end-capped PEA macromer (e.g., seeFIGS. 1, 2, 14, 18, 20, 22 and 25) is also provided.

A composition comprising a functional PEA macromer is also provided,wherein the functional PEA macromer comprises a terminal functionalgroup at each of the two ends of the macromer, wherein the terminalfunctional group is nucleophilic or electrophilic. In an embodiment, theterminal functional group is selected from the group consisting ofhydroxyl, amine, sulfonic acid, carboxyl, thiol, acryloyl and vinylgroups. In another embodiment, the terminal functional group ishydroxyl. and the macromer has a chemical formula described by thegeneral structural formula of Macromer 2.2, Macromer 5.2 orOH-Macromer-OH in Scheme 3. In another embodiment, the terminalfunctional group is amine and the macromer has a chemical formuladescribed by the general structural formula of NH2-Macromer-NH2 inScheme 3 or Macromer 6.1 in Scheme 6. In another embodiment, theterminal functional group is sulfonic acid and the macromer has achemical formula described by the general structural formula of Macromer4.2 in Scheme 4. In another embodiment, the terminal functional group iscarboxyl and the macromer has a chemical formula described by thegeneral structural formula of HOOC-Macromer-COOH in Scheme 3. In anotherembodiment, the terminal functional group is thiol and the macromer hasa chemical formula described by the general structural formula ofSH-Macromer-SH in Scheme 3. In another embodiment, the terminalfunctional group is acryloyl or vinyl and the macromer has a chemicalformula described by the general structural formula of Macromers 1.2,2.3, 5.3, 6.2 or 7.2.

A composition comprising a functional Arg-based monomer is alsoprovided, wherein the Arg-based monomer comprises an active double bondat each of the two ends of the monomer. A method for synthesizing afunctional PEA macromer is also provided, wherein the method comprisesproviding a nitrophenol end-capped PEA macromer, wherein:

the functional PEA macromer comprises a terminal functional group ateach of the two ends of the macromer, and the terminal functional groupis selected from the group consisting of hydroxyl, amine, sulfonic acid,carboxyl, thiol, acryloyl and vinyl groups. A composition comprising aPhe-EG based functional macromer is also provided. A method forsynthesizing a Phe-EG based functional macromer comprising the steps setforth in Scheme 1 is also provided. A composition comprising a Phe-basedfunctional macromer is also provided. A method for synthesizing aPhe-based functional macromer comprising the steps set forth in Scheme 2is also provided.

In an aspect the present invention provides a method of makingfunctional PEA macromers. For example, the nitrophenol end-capped PEAmacromer intermediates (Macromer 1.1 or 2.1) shown in FIG. 12 (Scheme3.1) and FIG. 13 (Scheme 3.2) can serve as activated precursors for thepreparation of additional functionalized PEA-based macromers having awide range of functional end-groups.

FIG. 12 (Scheme 3.1) illustrates the synthesis of exemplary PEA-basedmacromer derivatives based on Macromer 2.1. By reacting Macromer 2.1with glycine, ethylenediamine, 2-aminothanol and cysteamine, additionalfunctionalized PEA-based macromers having carboxyl, amine, hydroxyl andthiol end-groups, respectively, can be obtained, as shown in Scheme 3.1.OH-Macromer-OH and SH-Macromer-SH are two examples of such functionalPEA macromers that can be obtained.

A method for synthesizing a functional macromer comprising the steps setforth in Scheme 3.1 is also provided. A method for synthesizing a PEAhomopolymer or copolymer comprising the steps set forth in Scheme 3.2 isalso provided. A composition comprising a sulfonic acid-terminatedunsaturated functional PEA macromer is also provided. A method forsynthesizing a sulfonic acid-terminated unsaturated functional PEAmacromer comprising the steps set forth in Scheme 4 is also provided. Acomposition comprising an Arg-Based Macromer 5.3 is also provided. Amethod for synthesizing an Arg- Based Macromer 5.3 is also provided,wherein the macromer comprises a functional double bond end group, andwherein the method comprises the steps set forth in Scheme 5. Acomposition comprising an Arg-based Macromer 6.2 is also provided. Amethod for synthesizing an Arg-based Macromer 6.2, is also provided,wherein the macromer comprises a functional double bond end group, andwherein the method comprises the steps set forth in Scheme 6. Acomposition comprising an Arg-based Macromer 7.2 is also provided.

A method for synthesizing an Arg-based Macromer 7.2 is also provided,wherein the macromer comprises a functional double bond end group, andwherein the method comprises the steps set forth in Scheme 7. A methodfor synthesizing a functional Arg-based monomer is also provided,wherein the Arg-based monomer comprises active double bonds at the twoends of the monomer, and wherein the method comprises the steps setforth in Scheme 8.

In an aspect the present invention provides uses of PEA macromers.Functional PEA macromer 2.2 can be used, for example, as amacroinitiator to prepare block copolymers with polylactide andpoly(ε-caprolactone). Functional PEA macromer 2.3 (with acryloylend-groups) can gel by itself using standard photo (e.g., UV)crosslinking It can also be made into a hybrid hydrogel by crosslinkingwith PEG diacrylate, polysaccharide acrylate (e.g., as disclosed inPCT/US2009/002017) or unsaturated PEAs (U.S. application Ser. No.11/587,530). These hydrogels can be used for tissue engineeringscaffolds or as carriers for biomolecules. The unsaturated PEA macromerwith sulfonic acid end-groups can gel with PEG diacrylate. Such anionichydrogel products can be used as biologic carriers, e.g., positivecharged growth factors. They can also be used as the components of asynthetic extracellular matrix. Functional PEA Macromer 5.3 can formcationic hybrid hydrogels. In one embodiment, the cationic properties ofthe functional PEA Macromer 5.3 permit it to deliver biologics orbiomolecules.

Functional PEA macromers with thiol end-groups (SH-Macromer-SH) can beused to covalently link gold nano particles. Functional PEA macromerswith amine end-groups (H₂N-Macromer-NH₂) can be used as macroinitiatorsto prepare block copolymers with aliphatic polyesters such aspolylactide and poly(ε-caprolactone) via ring-opening polymerization.

A method for controlling release of a molecule or compound is alsoprovided, wherein the method comprises: providing a hydrogel, wherein:the molecule or compound is loaded in the hydrogel, and the hydrogel issynthesized from a functional PEA macromer. A method for directingrelease of a molecule or compound in an area of interest is providedcomprising: providing a hydrogel, wherein: the molecule or compound isloaded in the hydrogel, the hydrogel is synthesized from a functionalPEA macromer, and the hydrogel is inserted in the area of interest. Inone embodiment, the molecule or compound is a bioactive molecule orcompound. In another embodiment, the molecule or compound is a nutrient,pharmaceutical, drug, peptide, polypeptide, oligonucleotide orpolynucleotide.

An apparatus for controlling release of a molecule or compoundcomprising a hydrogel is also provided, wherein: the molecule orcompound is loaded in the hydrogel, and the hydrogel is synthesized froma functional PEA macromer. An apparatus for directing release of amolecule or compound in an area of interest comprising a hydrogel isalso provided, wherein: the molecule or compound is loaded in thehydrogel, the hydrogel is synthesized from a functional PEA macromer,and the hydrogel is inserted in the area of interest.

The following examples are presented to illustrate the presentinvention. They are not intended to limiting in any manner.

EXAMPLE 1

Example of Preparation of Phe-EG based Functional Macromer

A Phe-EG based functional macromer is provided. A method forsynthesizing a Phe-EG based functional macromer is also provided. FIG. 1(Scheme 1) shows an embodiment of the method for synthesizing a Phe-EGbased functional macromer in which Macromer 1.1 intermediate andMacromer 1.2 are synthesized from NPEG and Phe4EG. NPEG is one of themonomers used to polymerize PEA macromers and polymers. NPEG monomer isformed by the reaction of dicarboxylic acyl chlorides and p-nitrophenol.

Macromer 1.1, an intermediate product, was prepared by using the samesynthesis route as for making poly(ester amide) (PEA). In comparisonwith PEA polymers, PEA macromers have the same chemical structure butlower molecular weight. Macromer 1.1 differs from NPEG monomer in thatMacromer 1.1 has PEA structure but NPEG does not.

Steps of the Scheme 1 synthesis method are as follows. Synthesis ofPolyglycol 250 Acid Dichloride (FIG. 2). Polyglycol 250 (20 g, 0.08 mol)and an excess of thionyl chloride (18.91 g, 0.16 mol) were added into areaction flask. The reaction was then stirred under a nitrogenatmosphere at 60° C. for 16 hrs. Unreacted thionyl chloride was removedby vacuum distillation to obtain solid polyglycol 250 acid dichloride.To purify the crude product, polyglycol 250 acid dichloride wasdissolved in chloroform and then precipitated into ethyl ether. Thefinal products was isolated by centrifugation and dried in vacuo. Yieldwas 87%.

Synthesis of Di-p-nitrophenyl ester of Polyglycol 250 Diacid (NPEG)monomer (FIG. 3). A solution of triethylamine (12.12 g, 0.12 mol) andp-nitrophenol (16.70 g, 0.12 mol) in 300 mL of acetone was added into areaction flask with stir bar and a dropping funnel at 0° C. A solutionof polyglycol 250 acid dichloride (15 g, 52.3 mmol) in 100 mL acetonewas subsequently added drop wisely into the flask with rapidly stirringfor 3 hrs at 0° C. (ice/water bath) and then kept stirring at roomtemperature overnight. The reaction mixture was precipitated into waterand isolated by filtration. The crude product (NPEG) was purified byrecrystallizing in ethyl acetate for 3 times, and dried in vacuo. Yieldwas 74%

Synthesis of Di-p-toluenesulfonic Acid Salts of Bis-L-phenylalanineTetraethylene Glycol Ester (Phe4EG) monomer (FIG. 4). L-phenylalanine(25.87 g, 0.176 mol), p-toluenesulfonic acid monohydrate (33.44 g, 0.176mol) and tetraethylene glycol (15.54 g, 0.08 mol) in 300 mL of toluenewere placed in a reaction flask with a Dean-Stark apparatus and stirbar. The solid-liquid reaction mixture was heated to reflux for 24 hrsand then cooled to room temperature. After the solvent was removed byevaporation, the crude product was purified by recrystallizing inisopropyl alcohol 3 times and dried in vacuo.

Synthesis of Macromer 1.1 intermediate and Macromer 1.2 from NPEG andPhe4EG (FIG. 1). FIG. 1 (Scheme 1) shows the synthesis of Macromer 1.1intermediate from NPEG and Phe4EG. NPEG (4.643 g, 1.00×10-2 mol) andPhe4EG (5.553 g, 6.67×10-3 mol) were dissolved in DMA (4 g), and thentriethylamine (2.2 g, 2.20×10-2 mol) was added dropwise to the solution.The reaction mixture was heated to 80° C. for 24 hrs. The resultingmacromer solution was subsequently cooled to room temperature andprecipitated with cold ethyl acetate. The purification was performed bydissolving macromer in chloroform and then precipitating into ethylacetate solution again. The macromer residue was dried in vacuo at 50°C., which yielded a brown sticky product. Yield was 65%.

FIG. 1 (Scheme 1) also shows the synthesis of Macromer 1.2. Allylamine(0.12 g, 2.16×10-3 mol) in DMA (4 g) was added dropwise to a solution ofmacromer I (2.0 g, 1.08×10-3 mol) in 8 g DMA. The reaction was kept atroom temperature with stirring for 12 hrs. The purification procedurewas the same as described in the preparation of macromer 1.1. TheMacromer 1.2 was dried in vacuo at room temperature for 24 hrs. Thefinal product was still sticky brown with a 73% yield.

Characterization

The ¹H NMR spectrum (FIG. 5) for Macromer 1.2 showed two small peaks forthe vinyl protons (—CH═CH2) at δ 5.31 ppm and δ 5.87 ppm that were notfound in the Macromer 1.1 intermediate. This result confirmed thechemical structure of Macromer 1.2 showed in Scheme 1. Solubility dataare shown in Table 1.

TABLE 1 Solubility of Macromer 1.2 at room temperature (25° C.). EthylH₂O DMF DMSO THF Methanol acetate Chloroform Acetone Macromer 1.2± + + + + − + ± + soluble; − insoluble; ± partially soluble or swelling

EXAMPLE 2 Example of Preparation of Phe-Based Functional Macromer

A Phe-based functional macromer is provided. A method for synthesizing aPhe-based macromer is also provided. FIG. 6 (Scheme 2) shows anembodiment of the method for synthesizing Phe-based macromer in whichMacromer 2.1 intermediate, Macromer 2.2 and Macromer 2.3 aresynthesized. These Phe-based macromers differ from the Phe-EG-basedfunctional Macromers 1.1 and 1.2 (above, Section 5.1.) in the diol unit.Steps of the Scheme 2 synthesis method are as follows.

Synthesis of Di-p-toluenesulfonic Acid Salt of Bis-L-phenylalanineButane-1,4-diester Monomer (Phe-4) (FIG. 7). L-Phenylalanine (42.95 g,0.26 mol) and 1,4-butanediol (10.80 g, 0.12 mol) were directly condensedin refluxed toluene (500mL) with the presence of p-toluenesulfonic acidmonohydrate (57.00 g, 0.30 mol). The heterogeneous solid-liquid reactionmixture was heated to 120° C. and reflux for 24 hours until 14.90 mL(0.83 mol) of water collected by Dean-Stark apparatus. The resultingreaction mixture was cooled down to room temperature. The precipitatewas filtered on a Buchner funnel and then purified by recrystallizingthree times in water, filtered again and dried in vacuo. Yield was 68%.

Synthesis of Di-p-nitrophenyl Sebacate Monomer (NS) (FIG. 8). A solutionof p-nitrophenol (43.00 g, 0.31 mol) and triethylamine (43.13 mL, 0.31mol) dissolved in 500 mL acetone was placed in a single-neckround-bottom flask equipped with magnetic stirrer and a dropping funnel.The contents of the flask were kept at 0° C. by cooling with anice/water mixture. Sebacoyl chloride (28.54 mL, 0.13 mol) in 100 mL ofacetone was then added dropwise into the chilled solution withvigorously stirring for three hours and kept stirring at roomtemperature overnight. The resulting NS was precipitated in distilledwater, dried in vacuum at room temperature and then purified byrecrystallization from ethyl acetate three times. Yield was 75%.

Synthesis of Macromer 2.1 intermediate. NS (4.4420 g, 1.00×10-2 mol) andPhe-4 (6.0740 g, 8.33×10-3 mol) were dissolved in DMA (4 g), and thentriethylamine (2.2 g, 2.20×10-2 mol) was added dropwise to the solution.The reaction mixture was heated to 80° C. for 24 hrs. Subsequently, theresulting macromer solution was cooled to room temperature andprecipitated with cold ethyl acetate. The purification was performed bydissolved macromer in chloroform and precipitated into ethyl acetateagain. After removing ethyl acetate, the macromer residue was dried invacuo at 50° C. with 71% yield. Macromer 2.1 is similar to Macromer 1.1,except conventional diols are used instead of oligoethylene glycol inMacromer 1.1.

TABLE 2.1 Solubility of Macromer 2.1 at room temperature (25° C.) EthylH₂O DMF DMSO THF Methanol acetate Chloroform Acetone Macromer 2.1− + + + − − + − + soluble; − insoluble.

Synthesis of Functional PEA macromer 2.2 with functional —OH group.2-aminoethanol (0.15 g, 1.88×10-3 mol) in DMA (4 g) was added dropwiseto a solution of macromer 2.1(3.0 g, 9.39×10-4 mol) in 8 g DMA. Thereaction was kept at room temperature with stirring for 12 hrs. Thepurification procedure was the same as described in preparation ofmacromer 2.1. The macromer 2.2 was dried in vacuo at 50° C. for 24 hrs.The final product yield was 68%.

TABLE 2.2 Solubility of Macromer 2.2 at room temperature (25° C.). EthylH₂O DMF DMSO THF Methanol acetate Chloroform Acetone Macromer 2.2− + + + − − + − + soluble; − insoluble.

Synthesis of Functional PEA macromer 2.3 with functional acryloyl (>C═C<bond) group. Freshly distilled acryloyl chloride (0.18 g, 1.97'10-3 mol)in DMA (4 g) was added dropwise to a solution of Macromer 2.2 (1.5 g,4.93×10-4 mol) in 8 g DMA. The reaction was kept at room temperaturewith stirring for 12 hrs. The purification procedure was the same asdescribed in preparation of Macromer 2.1. Macromer 2.3 was dried invacuo at room temperature for 24 hrs. The final product had a 65% yield.

TABLE 2.3 Solubility of Macromer 2.3 at room Temperature (25° C.). EthylH₂O DMF DMSO THF Methanol acetate Chloroform Acetone Macromer 2.3− + + + − − + − + soluble; − insoluble.

Characterization

The chemical structure of the functional PEA macromers werecharacterized by standard NMR and FTIR methods. The ¹H NMR spectrum forMacromer 2.3 (FIG. 9) showed three small peaks for the protons of theacryloyl end groups: δ 5.92 ppm, δ 6.31 ppm (—CH═CH₂) and δ 6.18 ppm(—CH═CH₂) that were not found in the Macromer 2.1 intermediate andMacromer 2.2. These results confirmed the chemical structure of Macromer2.3 showed in Scheme 2.

The characteristic absorption bands of >C=C<groups (FIG. 10) wereobserved at 810 cm-1. This result indicated that the hydroxyl end groupsin Macromer 2.2 were converted to acryloyl groups in Macromer 2.3.

Hydrogel formation from Functional PEA macromer 2.3. An example ofmaking a gel from functional PEA Macromer 2.3 is provided. 0.20 g ofMacromer 2.3 was added to a vial and dissolved in 2 mL of DMSO to form aclear, homogeneous solution. Irgacure 2959 photoinitiator (0.02 g, 10 wt% of Macromer) was added into the Macromer solution 2.3. Subsequently,0.50 mL of this precursor solution was transferred into Teflon mold(diameter=12 mm, depth=4.4 mm) and irradiated by a UV lamp (365 nm,100W) for 20 minutes. The resultant hydrogel was removed and swelled inchloroform for 24 hours. FIG. 11 shows the optical images of gels madefrom functional PEA macromer 2.3.

EXAMPLE 3 Example of Preparation of Sulfonic Acid-terminated UnsaturatedFunctional PEA Macromer

A sulfonic acid-terminated unsaturated functional PEA macromer isprovided. A method for synthesizing a sulfonic acid-terminatedunsaturated functional PEA macromer is also provided. FIG. 14 (Scheme 4)shows an embodiment of the method for synthesizing Macromer 4.1intermediate and Macromer 4.2 according to one embodiment of the method.

Synthesis of Di-p-nitrophenyl Fumarate Monomer (NF). FIG. 15 shows thesynthesis of Di-p-nitrophenyl fumarate monomer (NF). A solution oftriethylamine (6.09 g, 0.0603 mol) and p-nitrophenol (8.39 g, 0.0603mol) in 100 mL of acetone was prepared at room temperature, and thesolution was kept at −78° C. with dry ice and ethanol. Fumaryl chloride(3.2 mL, 0.03 mol) in 40 mL of acetone was added drop wisely into thechilled solution, and then with stirring at room temperature overnight.The resulting NF was precipitated in distilled water, dried in vacuum atroom temperature and then purified by recrystallization fromacetonitrile three times. The yield obtained was 82%.

Synthesis of Di-p-toluenesulfonic Acid Salt of Bis-L-phenylalanineButane-1,4-diester Monomer (Phe-4). Di-p-toluenesulfonic Acid Salt ofBis-L-phenylalanine Butane-1,4-diester Monomer (Phe-4) was synthesizedas described above for Phe-Based Macromer (in Section 5.2).

Synthesis of Macromer 4.1 intermediate from NF and Phe-4. NF (3.5820 g,1.00×10-2 mol) and Phe (4.8530 g, 6.67×10-3 mol) were dissolved in DMA(4 g), and then triethylamine (2.2 g, 2.20×10-2 mol) was added dropwiseto the solution. The reaction mixture was heated to 80° C. for 24 hrs.Subsequently, the resulting macromer solution was cooled to roomtemperature and precipitated with cold ethyl acetate. The purificationwas performed by dissolved macromer in chloroform and precipitated intoethyl acetate again. After dumping the ethyl acetate, the macromerresidue was dried in vacuo at 50° C., with a 67% yield.

TABLE 4.1 Solubility of Macromer 4.1 at room Temperature (25° C.). EthylH₂O DMF DMSO THF Methanol acetate Chloroform Acetone Macromer 4.1 − + +− − − ± − + soluble; − insoluble; ± partially soluble or swelling

Synthesis of Macromer 4.2. Taurine (0.40 g, 3.15×10-3 mol) was addeddropwise to a solution of macromer 4.1 (2.0 g, 1.57×10-3 mol) in 8 gDMA. The reaction was maintained at 80° C. with stirring for 12 hrs. Thepurification procedure was the same as described above for thepreparation of Macromer 4.1 intermediate. Macromer 4.2 was dried invacuo at 50° C. for 24 hrs. The final product yield was 63%.

TABLE 4.2 Solubility of Macromer 4.2 at room Temperature (25° C.) EthylH₂O DMF DMSO THF Methanol acetate Chloroform Acetone Macromer 4.2 − + +− − − ± − + soluble; − insoluble; ± partially soluble or swelling

Characterization

FIG. 16 shows the 1H NMR spectra of Macromer 4.1 intermediate andMacromer 4.2. The new peaks at 6 3.53 ppm (—CH2-CH2SO-3H) (b) and at δ3.72 ppm (—CH2-CH2-SO3H) (a) in the 1H NMR spectrum of Macromer 4.2 wereattributed to the protons of methylene groups next to the sulfonic acidend groups.

Gel formation from Functional PEA macromer 4.2. In one embodiment, ahybrid gel can be synthesized from functional PEA macromer 4.2 andPEG-DA. A weight percentage ratio of 20/80 Macromer 4.2/PEG-750diacrylate (0.04 g of Macromer 4.2 and 0.16 g of PEG-750 diacrylate) wasadded to a vial and dissolved in 2 mL of DMSO to form a clear,homogeneous solution. A gel solution was made by adding the Irgacure2959 photoinitiator (0.02 g, 10 wt % of precursors) into the solution ofprecursors. Subsequently, 0.50 mL gel solution was poured into Teflonmold (diameter=12 mm, deepness=4.4 mm) and irradiated by a UV lamp (365nm, 100 W) for 20 minutes. The resultant hydrogel (with remainingresidual DMSO solvent) was removed and swelled in water for 2 hours.FIG. 17 shows optical images of such a hybrid gel before and afterswelling. The hybrid gel of FIG. 17 was made from sulfonicacid-terminated unsaturated functional PEA Macromer 4.2 and PEG-750diacrylate. (a: after removal from mold, b: after 2 hrs in water).

Gel formation from Functional PEA macromer 4.2. A hybrid gel can besynthesized from functional PEA macromer 4.2 and PEG-DA. A weightpercentage ratio of 20/80 Macromer 4.2/PEG-750 diacrylate (0.04 g ofMacromer 4.2 and 0.16 g of PEG-750 diacrylate) was added to a vial anddissolved in 2 mL of DMSO to form a clear, homogeneous solution. A gelsolution was made by adding the Irgacure 2959 photoinitiator (0.02 g, 10wt % of precursors) into the solution of precursors. Subsequently, 0.50mL gel solution was poured into Teflon mold (diameter=12 mm,deepness=4.4 mm) and irradiated by a UV lamp (365 nm, 100 W) for 20minutes. The resultant hydrogel (with remaining residual DMSO solvent)was removed and swelled in water for 2 hours. FIG. 17 shows opticalimages of such a hybrid gel before and after swelling. The hybrid gel ofFIG. 17 was made from sulfonic acid-terminated unsaturated functionalPEA Macromer 4.2 and PEG-750 diacrylate. (a: after removal from mold, b:after 2 hrs in water).

EXAMPLE 4

Example of Preparation Arg-Based Macromer 5.3 with Functional DoubleBond End Groups

An Arg-based macromer 5.3 with functional double bond end groups isprovided (FIG. 18). A method for synthesizing an Arg-Based Macromer 5.3with functional double bond end groups is also provided. FIG. 18 (Scheme5) shows an embodiment of the method in which Macromer 5.1 intermediate,Macromer 5.2 and Macromer 5.3 are synthesized. In one embodiment, thesteps of the method are as follows.

Synthesis of Di-p-toluenesulfonic Acid Salt of Bis-L-arginineButane-1,4-diester Monomer (Arg-4-S) (FIG. 19). FIG. 19 shows oneembodiment of the method for synthesizing Di-p-toluenesulfonic Acid Saltof Bis-L-arginine Butane-1,4-diester Monomer (Arg-4-S) (FIG. 19).L-arginine (45.29 g, 0.26 mol) and 1,4-butanediol (10.80 g, 0.12 mol)were directly condensed in refluxed toluene (500 mL) with the presenceof p-toluenesulfonic acid monohydrate (114.00 g, 0.60 mol). Theheterogeneous solid-liquid reaction mixture was heated to 120° C. andreflux for 24 hrs. The resulting reaction mixture was cooled down toroom temperature. The toluene was removed, and the crude product wasrecrystallized from isopropyl alcohol for three times before dried invacuo. Yield was 90%.

Synthesis of Macromer 5.1 intermediate (8-Arg-4 NP). NS (4.4420 g,1.00×10-2 mol) and Arg-4-S (8.1850 g, 7.5×10-3 mol) were dissolved inDMSO (4 g), and then triethylamine (2.2 g, 2.20×10-2 mol) was addeddropwise to the solution. The reaction mixture was heated to 80° C. for24 hrs. Subsequently, the resulting macromer solution was cooled to roomtemperature and precipitated with cold ethyl acetate. The purificationwas performed by dissolved macromer in methanol and precipitated intoethyl acetate again. After dumping the ethyl acetate, the macromerresidue was dried in vacuo at 50° C., yielded a brown sticky product,with a 78% yield.

TABLE 5.1 Solubility of Macromer 5.1 at room Temperature (25° C.) EthylH₂O DMF DMSO THF Methanol acetate Chloroform Acetone Macromer 5.1 ± + +− + − − − + soluble; − insoluble; ± partially soluble or swelling

Synthesis of Macromer 5.2. 2-aminoethanol (0.12 g, 1.87×10-3 mol) inDMSO (4 g) was added dropwise to a solution of macromer I (3.0 g,9.37×10-4 mol) in 8 g DMSO. The reaction was kept at room temperaturewith stirring for 12 hrs. The purification procedure was the same asdescribed in preparation of macromer 5.1 intermediate. Macromer 5.2 wasdried in vacuo at 50° C. for 24 hrs. The final product yield was 77%.

TABLE 5.2 Solubility of Macromer 5.2 at room Temperature (25° C.) EthylH₂O DMF DMSO THF Methanol acetate Chloroform Acetone Macromer 5.2 ± + +− + − − − + soluble; − insoluble; ± partially soluble or swelling

Synthesis of Macromer 5.3. Fresh distilled acryloyl chloride (0.18 g,1.97×10-3 mol) in DMF (4 g) was added dropwise to a solution of macromer5.2(1.5 g, 4.93×10-4 mol) in 8 g DMF. The reaction was kept at roomtemperature with stirring for 12 hrs. The purification procedure was thesame as described in preparation of macromer I. Macromer 5.3 was driedin vacuo at room temperature for 24 hrs. The final product yield was73%.

TABLE 5.3 Solubility of Macromer 5.3 at room Temperature (25° C.). EthylH₂O DMF DMSO THF Methanol acetate Chloroform Acetone Macromer 5.3 ± + +− + − − − + soluble; − insoluble; ± partially soluble or swelling

EXAMPLE 5

Example of Preparation Arg-Based Macromer 6.2 with Functional DoubleBond End Groups

Arg-Based Macromers 6.2 with functional double bond end groups areprovided (FIG. 20). A method for synthesizing Arg-Based Macromers 6.2with functional double bond end groups is also provided. Scheme 6 (FIG.20) shows one embodiment of the method, in which Macromer 6.1intermediate and Macromer 6.2 are synthesized.

Macromers 5.3 and 6.2 have similar chemical structures. However,Macromer 5.3 was synthesized from Macromer 5.1, which has nitrophenolend groups. The starting macromer for Macromer 6.2 was synthesized fromMacromer 6.1 which has amine end groups.

Synthesis of Macromer 6.1 intermediate. Arg-4-S (10.9130 g, 1×10-2 mol)and NS (2.9610 g, 6.67×10-3 mol) were dissolved in DMSO (4 g), and thentriethylamine (2.2 g, 2.20×10-2 mol) was added dropwise to the solution.The reaction mixture was heated to 80° C. for 24 hrs. The resultingmacromer solution was cooled to room temperature and precipitated withcold ethyl acetate. The purification was performed by dissolved macromerin methanol and precipitated into ethyl acetate again. After removingthe ethyl acetate, the macromer residue was dried in vacuo at 50° C.,which yielded a brown sticky product. Yield was 5%.

TABLE 6.1 Solubility of Macromer 6.1 at room Temperature (25° C.). EthylH₂O DMF DMSO THF Methanol acetate Chloroform Acetone Macromer 6.1 ± + +− + − − − + soluble; − insoluble; ± partially soluble or swelling

Synthesis of Macromer 6.2. NA (0.26 g, 1.33×10-3 mol) was added dropwiseto a solution of macromer I (2.0 g, 6.67×10-4 mol) in 8 g DMSO. Thereaction was kept at room temperature with stirring for 12 hrs. Thepurification procedure was the same as described in preparation ofArg-based macromer 6.1 intermediate. Arg-based macromer 6.2 was dried invacuo at room temperature for 24 hrs. The final product yield was 73%.

TABLE 6.2 Solubility of Macromer 6.2 at Room Temperature (25° C.). EthylH₂O DMF DMSO THF Methanol acetate Chloroform Acetone Macromer 6.2 ± + +− + − − − + soluble; − insoluble; ± partially soluble or swelling

Characterization

FIG. 21 shows the ¹H NMR spectrum for Macromer 6.2. The spectrum showsthree small peaks for the protons of the acryloyl end groups at δ 5.65ppm, δ 6.38 ppm (—CH═CH₂) and δ 6.12 ppm (—CH=CH₂).

EXAMPLE 5

Example of Preparation Arg-Based Macromer 7.2 with Functional DoubleBond End groups

An Arg-Based Macromer 7.2 with functional double bond end groups isprovided. A method for synthesizing an Arg-Based Macromer 7.2 withfunctional double bond end groups is also provided. Scheme 7 (FIG. 22)shows an embodiment of the method wherein Macromer 7.1 intermediate andMacromer 7.2 are synthesized.

Synthesis of Macromer 7.1 intermediate (8-Arg-4 NP). NS (4.4420 g,1.00×10-2 mol) and Arg-4-S (7.27 g, 6.67×10-3 mol) were dissolved inDMSO (4 g), and then triethylamine (2.2 g, 2.20×10-2 mol) was addeddropwise to the solution. The reaction mixture was heated to 80° C. for24 hrs. Subsequently, the resulting macromer solution was cooled to roomtemperature and precipitated with cold ethyl acetate. The purificationwas performed by dissolving macromer in methanol and precipitating intoethyl acetate again. After discarding the ethyl acetate, the macromerresidue was dried in vacuo at 50° C., yielded a brown sticky product in76% yield.

TABLE 7.1 Solubility of Macromer 7.1 at room Temperature (25° C.). EthylH₂O DMF DMSO THF Methanol acetate Chloroform Acetone Macromer 7.1 ± + +− + − − − + soluble; − insoluble; ± partially soluble or swelling

Synthesis of Macromer 7.2. Allylamine (0.10 g, 1.82×10-3 mol) in DMSO (4g) was added dropwise to a solution of macromer I (2.0 g, 9.09×10-4 mol)in 8 g DMSO. The reaction was kept at room temperature with stirring for12 hrs. The purification procedure was the same as described inpreparation of macromer I. The macromer II was dried in vacuo at roomtemperature for 24 hrs. The final product was in 73% yield.

TABLE 7.2 Solubility of Macromer 7.2 at room Temperature (25° C.). EthylH₂O DMF DMSO THF Methanol acetate Chloroform Acetone Macromer 7.1 ± + +− + − − − + soluble; − insoluble; ± partially soluble or swelling

Characterization

The ¹H NMR spectrum for Functional PEA macromer 6.2 (FIG. 23) showedthree small peaks for the protons of the acryloyl end groups at δ 5.66ppm, δ 6.38 ppm (—CH═CH₂) and δ 6.12 ppm (—CH═CH₂).

Gel formation from PEA function Macromer 7.2. An example of makinghybrid gel from Macromer 7.2 and PEG-DA is given here. A weightpercentage ratio of 20/80 Macromer 7.2/PEG-750 diacrylate (0.04 g ofMacromer 7.2 and 0.16 g of PEG-750 diacrylate) was added to a vial anddissolved in 2 mL of DMSO to form a clear, homogeneous solution. The gelsolution was made by adding Irgacure 2959 photoinitiator (0.02 g, 10 wt% of precursors) into the solution of precursors. Subsequently, 0.50 mLgel solution was added into Teflon module (diameter=12 mm, deepness=4.4mm) and irradiated by a UV lamp (365 nm, 100 W) for 20 minutes.

EXAMPLE 5 Example of Preparation of Functional Arg-Based Monomer

A functional Arg-based monomer is provided. A method for synthesizing afunctional Arg-based monomer is also provided. Scheme 8 (FIG. 25) setsforth one embodiment of the method, in which Monomer 8.1 is synthesized.Monomer 8.1 is not a macromer, but a functional monomer with an activedouble bond at each of the two ends of the monomer.

Synthesis of Monomer 8.1. Arg-4-S (10.9130 g, 1×10-2 mol) and NA (1.9300g, 1×10-2 mol) were dissolved in DMSO (4 g), and then triethylamine (2.2g, 2.20×10-2 mol) was added dropwise to the solution. The reactionmixture was heated to 80° C. for 24 hrs. The resulting macromer solutionwas cooled to room temperature and precipitated with cold ethyl acetate.The purification was performed by dissolving macromer in methanol andprecipitating into ethyl acetate again. After discarding the ethylacetate, the macromer residue was dried in vacuo at room temperature,yielding a brown sticky product at 73% yield.

Characterization

The ¹H NMR spectrum for Macromer 6.2 (FIG. 26) showed three small peaksfor the protons of the acryloyl end groups at δ 5.62 ppm, δ 6.37 ppm(—CH═CH₂) and δ 6.12 ppm (—CH═CH₂).

This functional PEA monomer is very unusual owing to the two activedouble bonds at the two ends of the monomer. It can be used as aPEA-based cross-linker to make hydrogels from PEA-based or non-PEA-basedprecursors. It can also be used to make polymers via free radicalpolymerization of the functional PEA monomer.

While the invention has been particularly shown and described withreference to specific embodiments (some of which are preferredembodiments), it should be understood by those having skill in the artthat various changes in form and detail may be made therein withoutdeparting from the spirit and scope of the present invention asdisclosed herein.

1. A macromer having the following structure:

wherein R¹ and R² at each occurrence in the macromer are independentlyselected from a C₁ to C₂₀ alkyl group, C₂ to C₂₀ alkenyl group, C₁ toC₂₀ alkyl diol group and C₄ to C₂₀ alkyl ether group, R³ is selectedfrom a C₁ to C₂₀ alkyl group, C₂ to C₂₀ alkenyl group, C₂ to C₂₀ alkyldiol group and C₄ to C₂₀ alkyl ether group, R⁴ and R⁵ at each occurrencein the macromer are independently a side-group of a naturally occurringamino acid or non-naturally occurring amino acid, E¹ and E² are eachindependently an end group, and n is an integer from 1 to
 20. 2. Themacromer of claim 1, wherein the macromer has the following structure:

wherein x is an integer from 1 to 10, y is an integer from 1 to 10, z isan integer from 1 to 10, u is an integer from 1 to 20, v is an integerfrom 1 to 20, w is an integer from 1 to 20, and t is an integer from 1to
 20. 3. A method for making a poly(ester amide) polymer comprising thesteps of: a) mixing a first macromer having the following structure:

wherein R¹ and R² at each occurrence in the macromer are independentlyselected from a C₁ to C₂₀ alkyl group, C₂ to C₂₀ alkenyl group, C₁ toC₂₀ alkyl diol group and C₄ to C₂₀ alkyl ether group, R³ is selectedfrom a C₁ to C₂₀ alkyl group, C₂ to C₂₀ alkenyl group, C₁ to C₂₀ alkyldiol group and C₄ to C₂₀ alkyl ether group, R⁴ and R⁵ at each occurrencein the macromer are independently a side-group of a naturally occurringamino acid or a non-naturally occurring amino acid, E¹ and E² are each a—COOH group, and n is an integer from 1 to 20, and a second macromerhaving the following structure:

R¹ and R² at each occurrence in the macromer are independently selectedfrom a C₁ to C₂₀ alkyl group, C₂ to C₂₀ alkenyl group, C₁ to C₂₀ alkyldiol group and C₄ to C₂₀ alkyl ether group, R³ is selected from a C₁ toC₂₀ alkyl group, C₂ to C₂₀ alkenyl group, C₁ to C₂₀ alkyl diol group andC₄ to C₂₀ alkyl ether group, R⁴ and R⁵ at each occurrence in themacromer are independently a side-group of a naturally occurring aminoacid or non-naturally occurring amino acid, E^(l) and E² are eachindependently a -NH₂ group or -OH group, and n is an integer from 1 to20, in a ratio of first macromer:second macromer of 0.5:1 to 2:1, andoptionally, a solvent; and b)mixing the mixture from a) with adehydrating agent until polymerization has proceeded to the desiredextent.
 4. A poly(ester amide) polymer having the following structure:

wherein R¹ and R² at each occurrence in the polymer are independentlyselected from a C₁ to C₂₀ alkyl group, C₂ to C₂₀ alkenyl group, C₁ toC₂₀ alkyl diol group and C₄ to C₂₀ alkyl ether group, R³ is selectedfrom a C₁ to C₂₀ alkyl group, C₂ to C₂₀ alkenyl group, C₁ to C₂₀ alkyldiol group and C₄ to C₂₀ alkyl ether group, R⁴ and R⁵ at each occurrencein the polymer are each independently a side-group of a naturallyoccurring amino acid or a non-naturally occurring amino acid, L¹ at eachoccurrence in the polymer are is independently an NH-linking group orO-linking group, E¹ and E² are each independently an end group, and n ateach occurrence in the polymer is an integer from 1 to 20, and m is aninteger from 2 to
 100. 5. The poly(ester amide) polymer of claim 4having the following structure:


6. A macromer having the following structure:

wherein R⁶ and R⁷ at each occurrence in the macromer are independentlyselected from a C₁ to C₂₀ alkyl group, C₂ to C₂₀ alkenyl group, C₁ toC₂₀ alkyl diol group and C₄ to C₂₀ alkyl ether group, R⁸ is a C₁ to C₂₀alkyl group, C₂ to C₂₀ alkenyl group, C₁ to C₂₀ alkyl diol group and C₄to C₂₀ alkyl ether group, R⁹ and R¹⁰ at each occurrence in the macromerare independently a side-group of a naturally occurring amino acid or anon-naturally occurring amino acid, R¹¹ and R¹² are each independently aside-group of a naturally occurring amino acid or a non- naturallyoccurring amino acid, E³ and E⁴ are each independently an end group, andj is an integer from 1 to
 20. 7. The macromer of claim 6, wherein themacromer has the following structure:

wherein p is an integer from 1 to 20, q is an integer from 1 to 20, andr is an integer from 1 to
 20. 8. A method for making a poly(ester amide)polymer comprising the steps of: a) mixing a first macromer having thefollowing structure:

wherein R⁶ and R⁷ at each occurrence in the macromer are independentlyselected from a C₁ to C₂₀ alkyl group, C₂ to C₂₀ alkenyl group, C₁ toC₂₀ alkyl diol group and C₄ to C₂₀ alkyl ether group, R⁸ is a C₁ to C₂₀alkyl group, C₂ to C₂₀ alkenyl group, C₁ to C₂₀ alkyl diol group and C₄to C₂₀ alkyl ether group, R⁹ and R¹° at each occurrence in the macromerare independently a side-group of a naturally occurring amino acid ornon-naturally occurring amino acid, R¹¹ and R¹² are each independently aside-group of a naturally occurring amino acid or non-naturallyoccurring amino acid, E³ and E⁴ are each a —COOH, and j is an integerfrom 1 to 20, and a second macromer having the following structure:

wherein R⁶ and R⁷ at each occurrence in the macromer are independentlyselected from a C₁ to C₂₀ alkyl group, C₂ to C₂₀ alkenyl group, C₁ toC₂₀ alkyl diol group and C₄ to C₂₀ alkyl ether group, R⁸ is a C₁ to C₂₀alkyl group, C₂ to C₂₀ alkenyl group, C₁ to C₂₀ alkyl diol group and C₄to C₂₀ alkyl ether group, R⁹ and R¹⁰ at each occurrence in the macromerare independently a side-group of a naturally occurring amino acid, R¹¹and R¹² are each independently a side-group of a naturally occurringamino acid, E³ and E⁴ are each independently a —NH₂ group or -OH group,and j is an integer from 1 to 20, in a ratio of first macromer:secondmacromer of 0.5:1 to 2:1, and optionally, a solvent; and b)mixing themixture from a) with a dehydrating agent until polymerization hasproceeded to the desired extent.
 9. A poly(ester amide) polymer havingthe following structure:

wherein R⁶, R⁷ and R⁸ at each occurrence in the polymer areindependently selected from a C₁ to C₂₀ alkyl group, C₂ to C₂₀ alkenylgroup, C₁ to C₂₀ alkyl diol group and C₄ to C₂₀ alkyl ether group, R⁹,R¹⁰, R¹¹ and R¹² at each occurrence in the macromer are independently aside-group of a naturally occurring amino acid or non-naturallyoccurring amino acid, L³ and L⁴ at each occurrence in the polymer areindependently an NH-linking group or O-linking group, E³ and E⁴ are eachindependently an end group, and j at each occurrence in the polymer isan integer from 1 to 20, and k is an integer from 2 to
 100. 10. A methodfor making a poly(ester amide) copolymer comprising the steps of: a)mixing a first macromer having the following structure:

wherein R¹ and R² at each occurrence in the macromer are independentlyselected from a C₁ to C₂₀ alkyl group, C₂ to C₂₀ alkenyl group, C₁ toC₂₀ alkyl diol group and C₄ to C₂₀ alkyl ether group, R³ is selectedfrom a C₁ to C₂₀ alkyl group, C₂ to C₂₀ alkenyl group, C₁ to C₂₀ alkyldiol group and C₄ to C₂₀ alkyl ether group, R⁴ and R⁵ at each occurrencein the macromer are independently a side-group of a naturally occurringamino acid or a non-naturally occurring amino acid, E¹ and E² are each a—COOH group, and n is an integer from 1 to 20, and a second macromerhaving the following structure:

wherein R⁶ and R⁷ at each occurrence in the macromer are independentlyselected from a C₁ to C₂₀ alkyl group, C₂ to C₂₀ alkenyl group, C₁ toC₂₀ alkyl diol group and C₄ to C₂₀ alkyl ether group, R⁸ is a C₁ to C₂₀alkyl group, C₂ to C₂₀ alkenyl group, C₁ to C₂₀ alkyl diol group and C₄to C₂₀ alkyl ether group, R⁹ and R¹⁰ at each occurrence in the macromerare independently a side-group of a naturally occurring amino acid or anon-naturally occurring amino acid, R¹¹ and R¹² are each independently aside-group of a naturally occurring amino acid or a non-naturallyoccurring amino acid, E³ and E⁴ are each independently a —NH₂ group or—OH group, and j is an integer from 1 to 20, or mixing a first macromerhaving the following structure:

wherein R⁶ and R⁷ at each occurrence in the macromer are independentlyselected from a C₁ to C₂₀ alkyl group, C₂ to C₂₀ alkenyl group, C₁ toC₂₀ alkyl diol group and C₄ to C₂₀ alkyl ether group, R⁸ is a C₁ to C₂₀alkyl group, C₂ to C₂₀ alkenyl group, C₁ to C₂₀ alkyl diol group and C₄to C₂₀ alkyl ether group, R⁹ and R¹⁰ at each occurrence in the macromerare independently a side-group of a naturally occurring amino acid or anon-naturally occurring amino acid, R¹¹ and R¹² are each independently aside-group of a naturally occurring amino acid or a non-naturallyoccurring amino acid, E³ and E⁴ are each a —COOH group, and a secondmacromer having the following structure:

R¹ and R² at each occurrence in the macromer are independently selectedfrom a C₁ to C₂₀ alkyl group, C₂ to C₂₀ alkenyl group, C₁ to C₂₀ alkyldiol group and C₄ to C₂₀ alkyl ether group, R³ is selected from a C₁ toC₂₀ alkyl group, C₂ to C₂₀ alkenyl group, C₁ to C₂₀ alkyl diol group andC₄ to C₂₀ alkyl ether group, R⁴ and R⁵ at each occurrence in themacromer are independently a side-group of a naturally occurring aminoacid or a non-naturally occurring amino acid, E^(l) and E² areindependently a —NH₂ group or —OH group, and n is an integer from 1 to20, in a ratio of first macromer:second macromer of 0.5:1 to 2:1, andoptionally, a solvent; and b)mixing the mixture from a) with adehydrating agent until polymerization has proceeded to the desiredextent.
 11. A poly(ester amide) copolymer having the followingstructure:

wherein R¹³, R¹⁴, R¹⁵, R¹⁶, R¹⁷, R¹⁸, R²⁵, R²⁶, R²⁷, R²⁸, R²⁹ and R³⁰ ateach occurrence in the polymer are independently selected from a C₁ toC₂₀ alkyl group, C₂ to C₂₀ alkenyl group, C₁ to C₂₀ alkyl diol group andC₄ to C₂₀ alkyl ether group, R¹⁹, R²⁰, R²¹, R²², R²³, R²⁴ and R³¹, R³²,R³³, R³⁴, R³⁵ and R³⁶ at each occurrence in the polymer areindependently a side-group of a naturally occurring amino acid or anon-naturally occurring amino acid, L⁵, L⁶, L⁷ and L⁸ at each occurrencein the polymer are independently an NH-linking group or O-linking group,E⁵, E⁶, E⁷ and E⁸ are each independently an end group, a at eachoccurrence in the polymer is an integer from 1 to 20, b at eachoccurrence in the polymer is an integer from 1 to 20, d at eachoccurrence in the polymer is an integer from 1 to 20, e at eachoccurrence in the polymer is an integer from 1 to 20, c is an integerfrom 2 to 100, and f is an integer from 2 to
 100. 12. (canceled) 13.(canceled)
 14. (canceled)
 15. (canceled)
 16. (canceled)